1. Technical Field of the Invention
The present invention relates to a film-forming method, a film-forming apparatus, an apparatus and a method for manufacturing a color filter substrate, an apparatus and a method for manufacturing a substrate for an electroluminescent device, a method for manufacturing a display device, a display device, and an electronic apparatus. More specifically, the present invention relates to a manufacturing technique for forming a film by supplying liquid material in a liquid drop state.
2. Description of the Related Art
In general, there are known a variety of display devices using as a display means an electro-optical apparatus such as a liquid crystal display device or an electroluminescent device (hereinafter, referred to as EL device), or an electronic apparatus, such as a cellular phone and a portable information terminal, in which such display device is built. As the color display has been in general use, such a display device commonly utilizes color filters formed in a predetermined arrangement patterns such as a stripe pattern, delta pattern, or mosaic pattern that consists of filter elements on red (R), green (G) and blue (B) dots on the surface of a substrate made of glass, plastic or the like.
Besides, in the EL device allowing color display, the red (R), green (G), and blue (B) dots of an EL light-emitting layer are arranged on the surface of a substrate made of glass, plastic or the like in a predetermined arrangement pattern such as stripe pattern, delta pattern or mosaic pattern, and such EL light-emitting layer is disposed between a pair of electrodes to thereby form a display dot. Then, a voltage applied to these electrodes is controlled for each display dot, so that each display dot emits light in a predetermined color and grayscale.
When manufacturing a variety of display devices as described above, photolithography is generally used for patterning respective colors of filter filaments of the color filter or respective colors of light-emitting layers of the EL device. However, the patterning process using photolithography requires several complicated, time-consuming processes such as coating, exposure and development of materials, and a large quantity of respective color materials or resists are consumed which leads to a problem of high costs.
In order to solve the aforementioned problem, a method for forming filter filaments or light-emitting layers arranged in a dot shape by adding solvent to filter element materials or EL light emitting materials to make a liquid material and discharging the liquid material as a liquid drop to be deposited to the surface of a substrate using an ink jet method, has been suggested. Here, according to the ink jet method, a case for forming filter elements 303 arranged in a dot shape, as shown in FIG. 29(b), inside a plurality of unit regions 302 set at the surface of a mother substrate 301, i.e., a large area of a substrate made of glass or plastic, as shown in FIG. 29(a), will be described.
In that case, for example, a liquid supplying head 306 having a nozzle row 305 of a plurality of nozzles 304, as shown in FIG. 29(c), is scanned along a straight line several times (twice in FIG. 29(b)) relative to a single unit region 302, as indicated by arrows A1 and A2 in FIG. 29(b). During each scanning period of time, ink or filter material is selectively discharged from a plurality of nozzles 304, thereby forming a filter element 303 at a desired position.
As described above, the filter elements 303 are arranged in a stripe pattern, delta pattern or mosaic pattern of respective colors, red (R), green (G), and blue (B). Therefore, in general, colors of red (R), green (G), and blue (B) are respectively prepared and respective liquid drop supplying heads 306 are utilized in sequence, thereby forming a color filter having a predetermined color arrangement on a mother substrate 301.
On the other hand, with regard to the liquid drop supplying heads 306, since there is a difference in the amount of ink depending upon a plurality of nozzles 304 consisting of a nozzle row 305, there may be a stripe pattern irregularity due to the difference of ink at respective filter elements 303 when the filter elements 303 are formed by the liquid drop supplying head 306 as shown in FIG. 29(b). As a result, there is a problem that the light transmissivity to a plane of a color filter is not uniform. Accordingly, there has been a method (for example, refer to Japanese Unexamined Patent Application Publication No. 2002-221616) in which respective filter elements are formed by discharging a plurality of liquid drops and the liquid drops are scanned in sequence as the position of the liquid drop supplying head 306 is moved little by little in the direction of sending liquid drops (the left and right directions in FIG. 29).
However, if a scanning process is performed in the aforementioned way, the number of scanning processes is rapidly increasing which makes the manufacturing time longer, thereby resulting in a problem of lowering production efficiency. Thus, in order to solve the aforementioned problem, an apparatus is suggested with a plurality of heads capable of adjusting of their positions mounted to a common carriage to widen its one-time scanning scope for an efficient manufacturing process (for example, refer to Japanese Unexamined Patent Application Publication No. 2002-273868).
However, the inventor found that it is impossible to eliminate a stripe pattern color irregularity in spite of the minimization of a difference in the amount of ink among respective filter elements in the aforementioned method if the color filter is manufactured in the conventional apparatus. As a result of continuous experiments, it has been found that the stripe pattern color irregularity is caused not by a difference in the amount of ink, but by a charge status of ink in respective filter elements. In other words, the deviated state of ink charged in the respective filter elements results in a difference in the amount of transmissive light depending upon places, which makes a stripe pattern of color irregularity noticeable.
FIG. 34 illustrates optical characteristics of a color filter manufactured in the conventional method. At this time, in FIG. 34(A), the vertical axis indicates Y value of transmissive light of the color filter (CIE1931XYZ color coordinate system, or brightness Y in the YUV color base), and the horizontal axis indicates periodic deviation characteristics of brightness Y seen in the scanning direction when the pixel array of the scanning direction (vertical direction as illustrated therein) illustrated in FIG. 29(b). Besides, as described above, FIG. 34(B) indicates periodic deviation characteristics as seen from the sending direction (horizontal direction as illustrated therein) illustrated in FIG. 29(b). Such deviation characteristics of brightness Y are not caused by a difference in the amount of ink due to the discharge characteristics of the head, but occurs even when a color filter is formed using a single nozzle.
Therefore, in the present invention, in order to solve the aforementioned problems, there is provided a technique to minimize the problem of irregularity in film formation which has not been solved by equalizing the amount of the liquid material to be supplied when a film-forming method is performed by depositing the liquid material on an object with a liquid drop supply means such as a liquid drop supply head.